Transcript 0934 MV local controller

Frankfurt (Germany), 6-9 June 2011
MV networks with Dispersed Generation:
voltage regulation based on local
controllers
Diana Moneta, Paolo Mora,
Massimo Gallanti
Gabriele Monfredini, Marco Merlo,
Valeria Olivieri
RSE - Italy
Politecnico di Milano - Italy
Diana Moneta – Italy – RIF4a – 0934
Frankfurt (Germany), 6-9 June 2011
Summary
DG effects on MV networks
 Local control strategies
 Case study - selection of ‘representative’
networks
 Hosting Capacity (HC) analysis
 Main results
 Final consideration

Frankfurt (Germany), 6-9 June 2011
DG effects on MV networks
the fast expanding of DG can affect
quality of supply as well as voltage quality
 more effective voltage regulation

 DG units as voltage control resources

Local control strategy: each generator
operates without coordination with other
devices and communication
infrastructures aren’t required.
Frankfurt (Germany), 6-9 June 2011
Local controller strategies


DG may inject active power at not-unitary power
factor, absorbing reactive power in order to
mitigate the voltage profile
Power Factor regulation of DG units once voltage
at PCC reaches defined thresholds.
Local voltage control strategy A
Droop control
Local voltage control strategy B
Fixed power factor
Frankfurt (Germany), 6-9 June 2011
Case study

A realistic distribution network with radial structure
(based on real network data) has been adopted
• The two main feeders are
modelled in detail
• Three DG units for each
feeder are considered


It can be expected that the feeder with an high(er)
voltage profile entails low margin to connectable
capacity
Impact of the voltage control was quantified for
multi-generator scenarios (realistic situation) on the
most critical feeder (lower nodal HC)
Frankfurt (Germany), 6-9 June 2011
Hosting Capacity analysis




minimum load condition (where the impact of DG
injections on voltage profile is more critical)
parametric study based on load flow simulations
control strategy ‘B’ (fixed power factor)
Feeder 4 - minimal nodal HC (2.11 MW)
Voltage and thermal constraints
Scenarios
(strategy ‘A’)
cos φ=1
PHC [MW]
cos φ=0.95
PHC [MW]
cos φ=0.9
PHC [MW]
#1
8.08
8.08
8.04
#2
5.49
8.02
8.02
#3
4.43
6.96
7.98
#4
3.8
6.12
7.92
#5
3.17
5.7
7.82
#6
2.53
5.28
7.57
• The total active power injection (up
to 10 MW) and the power
distribution along the 3 ‘equivalent’
generators were modulated.
• Slow voltage variation and thermal
constraint were considered
thermal limit

Frankfurt (Germany), 6-9 June 2011
Hosting capacity analysis - results



Improvement in network operation: fulfillment of
limits related to supply voltage variations, within
the range set by EN 50160 – but higher losses
due to the generators operating at not-unitary
power factor.
Over-voltages always occur in the last bus of the
feeder so only the power factor of DG unit
installed at the end of the feeder is changed.
Unlike usually expected, feeders with small
voltage drop in passive condition do not always
have high capacity of DG penetration.
Frankfurt (Germany), 6-9 June 2011
Final considerations and future developments
In case of over-voltage the reactive power
absorption by generators allows to
significantly increase DG penetration itself
 In some circumstances, thermal
constraints limit HC increasing
 It is necessary to define new criteria to
identify test network with critical features,
for example based on lower nodal Hosting
Capacity
 Design of the voltage control law

Frankfurt (Germany), 6-9 June 2011
Contacts

Marco MERLO
Politecnico di Milano – Italy
[email protected]

Diana MONETA
RSE – Italy
[email protected]